There is an increasing demand for changing wired data transmission to wireless data transmission. The use of wireless communication has already started in communications between a digital still camera (hereinafter referred to as a DSC) and peripheral devices such as a printer. The adoption of such wireless communication eliminates the necessity of cable installation and increases flexibility in setting locations of respective devices, thus improving portability.
In the IEEE 802.11 standard, there are two communication modes for communication between plural wireless terminals: the Infrastructure mode where communication is performed through a base station (access point, hereinafter referred to as an AP); and an Adhoc mode where wireless terminals directly communicate with each other without an intermediation of a particular AP.
Described hereinafter with reference to the drawings is, in particular, a connection method of wireless communication devices in the conventional Adhoc mode (a direct communication mode in which each device directly communicates each other without using a relay station).
FIG. 1 depicts a view showing as an example a construction of a wireless communication system where data transmission in the Adhoc mode is performed.
In FIG. 1, DSCs 101 to 104 and printers 105 and 106 respectively have a wireless communication function. In the wireless communication function, each device takes turns to generate at random a signal called “Beacon”, which notifies the peripheral wireless terminals of information necessary for the wireless communication, to realize synchronization, thereby enabling data transmission between DSCs, or between a DSC and the printer 105 or 106 using wireless communication means.
FIG. 2 depicts an explanatory view of a network connection method in the Adhoc mode.
Hereinafter, a description on an Adhoc network establishing method is described, assuming that the same Adhoc wireless communication parameters are set in advance in the printer 105 and the DSC 101 shown in FIG. 1. First, the power of the wireless communication unit of the printer 105 is turned on. The printer 105 then searches for an Adhoc network that has been constructed based on Adhoc wireless parameters set in advance (S201). The search method includes: searching for a “Beacon” signal, or broadcasting a control signal called a “Probe Request” and waiting for a response to the “Probe Request,” and the like. Herein, the latter method is adopted. The printer 105 broadcasts the “Probe Request” and waits for a response. In this example, an Adhoc network being searched does not exist. Therefore, even if the printer 105 transmits the “Probe Request” a predetermined number of times, the printer 105 cannot receive any “Probe Response.” Therefore, the printer establishes a network by itself and starts transmitting the “Beacon” (S202).
Next, when the power of the wireless communication unit of the DSC 101 is turned on, the DSC 101 transmits, similarly to the printer 105, a “Probe Request” to search for an Adhoc network constructed based on Adhoc wireless parameters set in advance (S203). In this stage, the network being searched by the DSC 101 has already been established by the printer 105. Therefore, the DSC 101 receives a “Probe Response” from the printer 105 (S204). The DSC 101 which has received the “Probe Response” acquires synchronized information and the like of the network that has been established by the printer 105, thereby realizing connection with the network (S205).
Next, in the construction shown in FIG. 1, a conventional method of searching, by a DSC, a data-transmission target printer is described in the flowchart of FIG. 3. Described herein is an example in which a new DSC is brought in to be connected to a printer (e.g., the printer 105) in an existing Adhoc wireless LAN communication system.
Referring to FIG. 3, in a case where a DSC is connected to a printer, first, a Service Set Identifier (SSID) is set in the DSC in step S301. In step S302, an encryption key is set, as needed, to prevent tapping in wireless communication. In step S303, an Adhoc mode is set as a wireless communication mode. In step S304, a device on the wireless network is searched. In step S305, a desired printer (herein, printer 105) is selected from the devices on the wireless network and wireless communication is established between the DSC and the printer.
The above-described method enables connection between the DSC and the printer 105 through wireless communication and enables direct image data transmission from the DSC to the printer 105 for printing. In this case, some kind of method is necessary to set the setting information necessary for wireless communication in both the DSC and the printer 105. The method includes, for instance, registering in advance an SSID and an encryption key in the printer 105 or the DSC before product shipping, and connecting the DSC to the printer 105 using a USB cable to set the SSID and encryption key in the DSC. The control processing of the printer 105 in this case is shown in the flowchart of FIG. 4.
First in step S401, the printer 105 is connected to the DSC using a USB cable. In step S402, the printer 105 transmits a request command to determine whether or not the DSC comprises wireless communication means. In step S403, if the printer 105 does not receive any response from the DSC after an elapse of predetermined time period after the step S402, it determines that the DSC connected has no wireless communication means, and the control ends. If a response is received, the control proceeds to step S404 for confirming the contents of the response, and then it is determined whether or not the DSC comprises wireless communication means. If it is determined that the DSC does not comprise wireless communication means, the control ends. If it is determined that the DSC comprises wireless communication means in the step S04, the control proceeds to step S405, and the wireless communication setting information of the printer 105 is transmitted to the DSC.
The above-described method enables setting of the common setting information necessary for wireless communication in both the printer 105 and the DSC, and enables wireless communication between the printer 105 and the DSC according to the setting information. Besides, for communication means in the Adhoc mode, there is a following technique used in a network configured with a master station and a slave station. The slave station transmits a capability value of the slave station to the master station, and the master station selects a backup master as a next master station candidate based on parameters of respective slave stations. Then, backup master information, which includes an address of the selected backup master and synchronized information, is provided to the respective slave stations. According to this technique, a network can reliably be established even if the master station is gone (refer to Japanese Patent Application KOKAI No. 2004-129042).
However, according to the above-described conventional example, the following problem may occur in the method of registering an SSID and an encryption key in a printer before product shipping and connecting the printer to a DSC using a USB cable to set the SSID and encryption key in the DSC. More specifically, if a DSC is erroneously connected to the printer, contrary to user's intention the SSID and encryption key are set in the DSC in accordance with information set in the printer, overwriting the effective SSID and encryption key stored originally in the DSC.
Furthermore, another problem occurs in the method of registering an SSID and an encryption key in a DSC before product shipping and connecting the DSC to a printer using a USB cable to set the SSID and encryption key in the printer. That is, each time a DSC is connected to a printer, the printer's SSID and encryption key are changed. Moreover, the setting operation of wireless parameters is cumbersome to users.